Simultaneous velocity-temperature measurements in the heated wake of a cylinder with implications for the modeling of turbulent passive scalars

Two principal quantities of interest in applications of scalar mixing in turbulent flows are the mean scalar and the scalar variance. Reynolds-averaged approaches are computationally efficient numerical methods that predict these fields. They require, however, the introduction of models to close the governing equations. Oftentimes, the numerical constants employed in these models include, or depend upon, the turbulent Prandtl number (PrT) and the mechanical-to-thermal time-scale ratio (r), which are generally assumed to be constant, but flow dependent. The present work studies the sensitivity of PrT and r to differences in their injection method within the same flow. To this end, mixed velocity-temperature statistics were measured in the wake of a circular cylinder. The wake was heated by one of two ways: heating the cylinder or heating an array of fine parallel wires (called a mandoline) placed downstream of the cylinder. The experimental results demonstrate that the magnitude of PrT varies throughout th...